Crystalline Thorium Borate

Abstract

Crystalline thorium borate (ThB 2 O 5 ) has been synthesized by the reaction of thoria with boric oxide at elevated temperatures; crystals of size suitable for single‐crystal X‐ray studies were grown in molten boric oxide at 1300°C. Crystallographic, chemical, and some physical properties of thorium borate crystals are presented as well as the results of a preliminary phase study of the system ThO 2 ‐B 2 O 3 . Amorphous thorium borate gel, formed by reaction of aqueous solutions of borax and thorium nitrate, is transformed into crystalline thorium borate and thoria on firing at elevated temperatures. Boric oxide does not appear to react with either zirconium oxide or uranium dioxide to form any crystalline compounds. The fact that uranium dioxide does not react with boric oxide, but thoria does, affords a basis for effecting a chemical separation of the two oxides from thoria‐urania solid solutions. Preliminary data on the reactions between boric oxide and different thoria‐urania solid solutions are given.